Vibration element, physical quantity sensor, inertial measurement unit, electronic apparatus, and vehicle

ABSTRACT

A vibration element includes a base and a vibrating arm extending from the base. The vibrating arm includes an arm positioned between the base and a weight. A weight film is disposed on the weight. The weight has a first principal surface and a second principal surface in a front and back relationship with respect to a center plane of the arm. A center of gravity of the weight is located between the first principal surface and the center plane of the arm. A center of gravity of the weight film is located between the second principal surface and the center plane of the arm.

CROSS-REFERENCE

This application is a continuation application of U.S. patentapplication Ser. No. 17/243,632 filed Apr. 29, 2021, which is acontinuation application of U.S. patent application Ser. No. 16/253,712filed on Jan. 22, 2019, now U.S. Pat. No. 11,025,222 issued on Jun. 1,2021, which claims the benefit of priority from, JP Application No.2018-009173, filed Jan. 23, 2018. The entire disclosures of the aboveapplications are incorporated herein by reference.

BACKGROUND 1. Technical Field

The present invention relates to a vibration element, a manufacturingmethod of the vibration element, a physical quantity sensor, an inertialmeasurement device, an electronic apparatus, and a vehicle.

2. Related Art

In the related art, a vibration element used for a device such as aquartz crystal vibrator, a vibration type gyro sensor, or the like isknown. A tuning fork type quartz crystal vibrator element described inJP-A-2006-311444, which is an example of such a vibration element,includes a base and a pair of vibrating arms which are bifurcated fromthe base and extend parallel to each other. Here, the tip end of thevibrating arm is provided with a weight which is processed to athickness thinner than a thickness of an arm of the vibrating arm, and ametal film for adjusting a frequency of the tuning fork type quartzcrystal vibrator element is provided in the weight. A tuning fork typepiezoelectric vibrator element described in JP-A-2010-213262 includes abase and a pair of vibrating arms which are bifurcated from the base andextend parallel to each other, and a portion whose thickness is thinnerthan a predetermined thickness is formed in a weight at the tip end ofwhich the width is enlarged greater than the width of the arm of thevibrating arm. In the weight, a metal film used for frequency adjustmentis provided on both the upper and lower surfaces of the weight.

However, in the tuning fork type quartz crystal vibrator elementsdescribed in JP-A-2006-311444 and JP-A-2010-213262, since the center ofgravity of a structure composed of the weight and the metal film isshifted in the thickness direction with respect to a center plane in thethickness direction of the arm of the vibrating arm, when the pair ofvibrating arms vibrate in a direction (in-plane direction) ofapproaching or separating from each other, the vibrating arms generatevibrations including a direction component in the thickness direction(out-of-plane direction), and as a result, there is a problem that thevibration component in the thickness direction leaks to the outside ofthe vibration element via the base and becomes a noise vibration sourceto the outside of the vibration element.

SUMMARY

An advantage of some aspects of the invention is to provide a vibrationelement capable of reducing noise vibration to the outside of thevibration element and a method of manufacturing the vibration element,and also to provide a physical quantity sensor, an inertial measurementdevice, an electronic apparatus, and a vehicle.

The invention can be implemented as the following application examplesor forms.

A vibration element according to an application example includes a base,a vibrating arm which extends from the base and includes an armpositioned on the base side and a weight positioned closer to a tip endside than the arm, a weight film disposed on the weight, and in whichthe weight has a first principal surface and a second principal surfacein a front and back relationship with respect to a thickness directionof the vibration element, a center of gravity of the weight is at aposition closer to the first principal surface side than to a centerplane of the arm in the thickness direction, and a center of gravity ofthe weight film is at a position closer to a second principal surfaceside than to the center plane of the arm in the thickness direction.

According to such a vibration element, since the center of gravity ofthe weight is at a position on the first principal surface side than tothe center plane of the arm in the thickness direction whereas thecenter of gravity of the weight film is at a position on the secondprincipal surface side than to the center plane of the arm in thethickness direction, the center of gravity of a structure composed ofthe weight and the weight film can be brought close to the center plane(the center of the vibrating arm in the thickness direction). For thatreason, it is possible to reduce unnecessary vibration (vibrations inthe thickness direction) of the vibrating arm, and as a result, it ispossible to reduce noise vibration to the outside of the vibrationelement.

In the vibration element according to the application example, it ispreferable that the weight includes a first portion and a second portionhaving a thickness thinner than that of the first portion, and thesecond principal surface has a stepped shape formed by the first portionand the second portion.

With this configuration, the center of gravity of the weight may bepositioned closer to the first principal surface side than to the centerplane of the arm in the thickness direction with a relatively simpleconfiguration.

In the vibration element according to the application example, it ispreferable that the weight has a portion in which the thicknessgradually decreases between the first portion and the second portion ina plan view in the thickness direction of the weight.

With this configuration, the weight film may be formed easily andcontinuously over the first portion and the second portion. In addition,occurrence of cracks in the weight film due to a step difference betweenthe first portion and the second portion may be reduced.

In the vibration element according to the application example, it ispreferable that a width of the weight is larger than a width of the armin a plan view in the thickness direction.

With this configuration, an area of the weight in which the weight filmcan be formed may be increased.

In the vibration element according to the application example, it ispreferable that the second portion is disposed on both sides in thewidth direction of the vibrating arm with respect to the first portion.

With this configuration, the torsional moment of the vibrating arm maybe reduced.

In the vibration element according to the application example, it ispreferable that the second portion is disposed on a side opposite to thebase with respect to the first portion.

With this configuration, the area of the second portion in a plan viewmay be reduced. Further, there is also an advantage that a mass balancein the width direction of the weight is hardly collapsed.

In the vibration element according to the application example, it ispreferable that the first portion is provided to surround the secondportion in a plan view in the thickness direction of the weight.

With this configuration, designing of the second portion is facilitated.

In the vibration element according to the application example, it ispreferable that the first principal surface is a flat surface.

With this configuration, it is not necessary to process the firstprincipal surface side of the weight in order to provide the firstportion and the second portion in the weight, and as a result, amanufacturing process of the vibration element may be simplified.

In the vibration element according to the application example, it ispreferable that the weight film is disposed on the first portion and thesecond portion.

With this configuration, it is possible to increase mass of the weightfilm. In addition, forming of the weight film may be simplified.

In the vibration element according to the application example, it ispreferable that the arm has a shape which is plane-symmetric withrespect to a center plane in a thickness direction of the arm.

With this configuration, vibration in the thickness direction due to theshape of the vibrating arm may be reduced.

In the vibration element according to the application example, it ispreferable that a first vibrating arm which extends from the base andserves as the vibrating arm including a first arm serving as the arm anda first weight serving as the weight, a second vibrating arm whichextends from the base and includes a second arm positioned on the baseside and a second weight positioned closer to the tip end side than thesecond arm, a first weight film which serves as the weight film disposedon the first weight, and a second weight film disposed on the secondweight are included, and a center of gravity of the second weight is ata position closer to the first principal surface side than to a centerplane of the second arm in the thickness direction, and a center ofgravity of the second weight film is at a position closer to the secondprincipal surface side than to the center plane of the second arm in thethickness direction.

With this configuration, unnecessary vibration (vibration in thethickness direction) of both the first vibrating arm and the secondvibrating arm may be reduced. In addition, since the centers of thefirst weight and the second weight are both positioned on the firstprincipal surface side (on the same side), and the centers of gravity ofthe first weight film and the second weight film are both positioned onthe second principal surface side (on the same side), it is easy to formthe weight and the weight film.

In the vibration element according to the application example, it ispreferable that a drive arm that is subjected to drive vibration, and adetection arm which deforms corresponding to an inertial force, areincluded, and the base includes a base main body and a connectorextending from the base main body, the drive arm serves as the vibratingarm and extends from the connector, and the detection arm extends fromthe base main body.

With this configuration, the characteristics of a so-called doubleT-type vibration element may be improved.

In the vibration element according to the application example, it ispreferable that a drive arm which extends from the base and is subjectedto drive vibration, and a detection arm which extends from the base in adirection opposite to the drive arm and deforms corresponding to aninertial force, are included, and the drive arm serves as the vibratingarm.

With this configuration, the characteristics of a so-called H-typevibration element may be improved.

In the vibration element according to the application example, it ispreferable that the weight film includes a first weight film and asecond weight film having a thickness thinner than the first weightfilm.

With this configuration, fine adjustment and coarse adjustment may beeasily performed when adjusting a resonance frequency of the vibratingarm by removing a part of the weight film by an energy ray such as alaser.

A manufacturing method of a vibration element according to anapplication example includes forming a base and a vibrating arm whichincludes a weight and extends from the base, has a first principalsurface and a second principal surface which are in a front and backrelationship with respect to a thickness direction, and of which acenter of gravity is positioned closer to the first principal surfaceside than to a center plane in the thickness direction, forming a weightfilm of which a center of gravity is positioned closer to the secondprincipal surface than to the center plane of the vibrating arm in thethickness direction on the vibrating arm, and adjusting a resonancefrequency of the vibrating arm by adjusting mass of the weight film.

According to such a manufacturing method of the vibration element, thecharacteristics of the obtained vibration element may be improved. Sinceit is sufficient to dispose the weight film only on one surface side ofthe weight (specifically, on the second principal surface side), it ispossible to simplify the manufacturing process of the vibrating elementand reduce a splash (dross) generated when the resonance frequency ofthe vibrating arm is adjusted by removing a part of the weight film bythe energy ray such as the laser.

A physical quantity sensor according to an application example includesthe vibration element of the application example, and a package whichaccommodates the vibration element.

According to such a physical quantity sensor, it is possible to improvethe sensor characteristics (for example, detection accuracy) of thephysical quantity sensor by utilizing the excellent characteristics ofthe vibration element.

An inertial measurement device according to an application exampleincludes the physical quantity sensor of the application example, and acircuit which is electrically connected to the physical quantity sensor.

According to such an inertial measurement device, it is possible toimprove the characteristics (for example, measurement accuracy) of theinertial measurement device by utilizing excellent sensorcharacteristics of the physical quantity sensor.

An electronic apparatus according to an application example includes thevibration element of this application example.

According to such an electronic apparatus, it is possible to improvecharacteristics (for example, reliability) of the electronic apparatusby utilizing the excellent characteristics of the vibration device.

A vehicle according to an application example includes the vibrationelement of this application example.

According to such a vehicle, it is possible to improve thecharacteristics (for example, reliability) of the vehicle by utilizingexcellent characteristics of the vibration element.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will be described with reference to theaccompanying drawings, wherein like numbers reference like elements.

FIG. 1 is a plan view illustrating a vibration element according to afirst embodiment of the invention.

FIG. 2 is a cross-sectional view taken along line A-A in FIG. 1 .

FIG. 3 is an enlarged plan view illustrating a weight and a weight filmof a vibrating arm (drive arm) of the vibration element.

FIG. 4 is a cross-sectional view taken along line B-B in FIG. 3 .

FIG. 5 is a cross-sectional view taken along line C-C in FIG. 3 .

FIG. 6 is a flowchart illustrating an example of a manufacturing methodof the vibration element.

FIG. 7 is a cross-sectional view illustrating a sub-step of preparing asubstrate in a vibrator element forming step.

FIG. 8 is a cross-sectional view illustrating a sub-step of forming acorrosion-resistant film and a resist film in the vibrator elementforming step.

FIG. 9 is a cross-sectional view illustrating a sub-step of forming anouter shape of the vibrator element in the vibrator element formingstep.

FIG. 10 is a cross-sectional view illustrating a sub-step of removing apart of the corrosion-resistant film in the vibrator element formingstep.

FIG. 11 is a cross-sectional view illustrating a sub-step of forming agroove portion in the vibrator element forming step.

FIG. 12 is a cross-sectional view illustrating a sub-step of removingthe corrosion-resistant film and the resist film in the vibrator elementforming step.

FIG. 13 is a cross-sectional view illustrating an electrode formingstep.

FIG. 14 is a cross-sectional view illustrating a weight film formingstep.

FIG. 15 is a cross-sectional view illustrating a frequency adjustingstep.

FIG. 16 is an enlarged plan view illustrating a weight and a weight filmof a vibrating arm (drive arm) of a vibration element according to asecond embodiment of the invention.

FIG. 17 is a cross-sectional view taken along line C-C in FIG. 16 .

FIG. 18 is an enlarged plan view illustrating a weight and a weight filmof a vibrating arm (drive arm) of a vibration element according to athird embodiment of the invention.

FIG. 19 is an enlarged plan view illustrating a weight and a weight filmof a vibrating arm (drive arm) of a vibration element according to afourth embodiment of the invention.

FIG. 20 is a cross-sectional view taken along line B-B in FIG. 19 .

FIG. 21 is a plan view illustrating a vibration element according to afifth embodiment of the invention.

FIG. 22 is a plan view illustrating a vibration element according to asixth embodiment of the invention.

FIG. 23 is a cross-sectional view illustrating a physical quantitysensor according to an embodiment of the invention.

FIG. 24 is an exploded perspective view illustrating an embodiment of aninertial measurement device according to the invention.

FIG. 25 is a perspective view of a substrate included in the inertialmeasurement device illustrated in FIG. 24 .

FIG. 26 is a perspective view illustrating an embodiment (a mobile type(or notebook type) personal computer) of an electronic apparatusaccording to the invention.

FIG. 27 is a plan view illustrating an embodiment (mobile phone) of theelectronic apparatus according to the invention.

FIG. 28 is a perspective view illustrating an embodiment (digital stillcamera) of the electronic apparatus according to the invention.

FIG. 29 is a perspective view illustrating an embodiment (automobile) ofa vehicle according to the invention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, a vibration element, a manufacturing method of thevibration element, a physical quantity sensor, an inertial measurementdevice, an electronic apparatus, and a vehicle according to theinvention will be described in detail based on embodiments illustratedin the accompanying drawings.

1. Vibration Element and Manufacturing Method Thereof

First Embodiment

First, a vibration element and a manufacturing method thereof will bedescribed.

Vibration Element

FIG. 1 is a plan view illustrating a vibration element according to afirst embodiment of the invention. FIG. 2 is a cross-sectional viewtaken along line A-A in FIG. 1 . FIG. 3 is an enlarged plan viewillustrating a weight and a weight film of a vibrating arm (drive arm)of the vibration element. FIG. 4 is a cross-sectional view taken alongline B-B in FIG. 3 . FIG. 5 is a cross-sectional view taken along lineC-C in FIG. 3 . In each drawing, the dimensions of parts are exaggeratedas deemed appropriate, and a dimensional ratio between the parts doesnot necessarily agree with an actual dimensional ratio. The position,direction, size, and the like of each unit described below also includea range of a manufacturing error and the like (for example, within arange of ±1% or less), and are not limited to the direction, size, andthe like described in the specification of the present application, aslong as desired functions of each part can be realized.

In the following description, for convenience of explanation, adescription will be made by appropriately using three axes of thex-axis, y-axis, and z-axis that are orthogonal to each other. In thefollowing, a direction parallel to the x-axis is referred to as an“x-axis direction”, a direction parallel to the y-axis is referred to asa “y-axis direction”, and a direction parallel to the z-axis is referredto as a “z-axis direction”. The tip end side of an arrow indicating eachof the x-axis, y-axis, and z-axis is assumed as “+”, and the base endside of the arrow is assumed as “−”. Also, the +z-axis direction side isreferred to as “upper”, the −z-axis direction side is referred to as“lower”, the +x-axis direction side is referred to as “right”, and the−x-axis direction side is referred to as “left”. Also, what is seen fromthe z-axis direction is referred to as a “plan view”. In FIG. 1 , forconvenience of description, illustration of an electrode film 4 whichwill be described later is omitted.

A vibration element 1 illustrated in FIG. 1 is a sensor element fordetecting an angular velocity around the z-axis. The vibration element 1includes a vibrator element 2 (see FIG. 1 ), an electrode film 4 (seeFIG. 2 ) disposed on the vibrator element 2, and a weight film 3 (seeFIG. 1 ) disposed on the electrode film 4.

As illustrated in FIG. 1 , the vibrator element 2 has a so-called doubleT-type structure. More specifically, the vibrator element 2 includes abase 21, a pair of detection arms 22 and 23 (first and second detectionarms) extending from the base 21, a pair of drive arms 24 and 25 (firstdrive arm), and a pair of drive arms 26 and 27 (second drive arm).

Here, the base 21 includes a base main body 211 supported by a package11 (see FIG. 23 ) which will be described later, a connecting arm 212extending from the base main body 211 along the +x-axis direction, and aconnecting arm 213 extending from the base main body 211 along the−x-axis direction opposite to the extending direction of the connectingarm 212. The detection arm 22 (first detection arm) extends from thebase main body 211 along the +y-axis direction intersecting with theextending direction of the connecting arms 212 and 213, whereas thedetection arm 23 (second detection arm) extends from the base main body211 along the −y-axis direction opposite to the extending direction ofthe detection arm 22. The drive arm 24 (first drive arm) extends fromthe tip end region of the connecting arm 212 along the +y-axisdirection, whereas the drive arm 25 (first drive arm) extends from thetip end region of the connecting arm 212 along the −y-axis directionopposite to the extending direction of the drive arm 24. Similarly, thedrive arm 26 (second drive arm) extends from the tip end region of theconnecting arm 213 along the +y-axis direction, whereas the drive arm 27extends from the tip end region of the connecting arm 213 along the−y-axis direction opposite to the extending direction of the drive arm26.

The detection arm 22 includes an arm 221 (detection arm link) extendingfrom the base main body 211, a weight 222 (detection weight) provided onthe tip end side with respect to the arm 221 and having a width largerthan that of the arm 221, and a groove 223 provided in each of the upperand lower surfaces of the arm 221. Similarly, the detection arm 23includes an arm 231 (detection arm link), a weight 232 (detectionweight), and a pair of grooves 233. The drive arm 24 includes an arm 241(drive arm link) extending from the connecting arm 212, a weight 242(drive weight) provided on the tip end side with respect to the arm 241and having a width larger than that of the arm 241, and a pair ofgrooves 243 provided in the upper and lower surfaces of the arm 241.Similarly, the drive arm 25 includes an arm 251 (drive arm link), aweight 252 (drive weight), and a pair of grooves 253. The drive arm 26includes an arm 261 (drive arm link) extending from the connecting arm213, a weight 262 (drive weight) provided on the tip end side withrespect to the arm 261 and having a width larger than that of the arm261, and a pair of grooves 263 provided in the upper and lower surfacesof the arm 261. Similarly, the drive arm 27 includes an arm 271 (drivearm link), a weight 272 (drive weight), and a pair of grooves 273.

At least one of the upper and lower grooves may be omitted in each ofthe pairs of grooves 223, 233, 243, 253, 263, and 273. Further, one pairof upper and lower grooves may be in communication with each other ineach of the grooves 223, 233, 243, 253, 263, and 273. That is, the arms221, 231, 241, 251, 261, and 271 may be provided with through holes(slots) which open on the upper and lower surfaces. The width of theweights 222, 232, 242, 252, 262, and 272 may be equal to or less thanthe width of the arms 221, 231, 241, 251, 261, and 271.

Here, the arm 221 is a portion that is bent (deformed) when thedetection arm 22 vibrates (during detection vibration), and is a portion(portion where the detection signal electrode 43 and the detectionground electrode 44, which will be described later, are provided) thatdetects electric charges generated by detection vibration of thedetection arm 22. Similarly, the arm 231 is a portion that bends(deforms) when the detection arm 23 vibrates (during detectionvibration), and is a portion (portion where the detection signalelectrode 43 and the detection ground electrode 44, which will bedescribed later, are provided) that detects electric charges generatedby detection vibration of the detection arm 23. The arm 241 is a portionthat is bent (deformed) when the drive arm 24 vibrates (during drivevibration), and is a portion (portion where the drive signal electrode41 and the drive ground electrode 42, which will be described later, areprovided) to which an electric field for driving the drive arm 24 isapplied. Similarly, the arms 251, 261 and 271 are portions that are bent(deformed) when the drive arms 25, 26 and 27 vibrate (during drivevibration), respectively, and are portions (portions where the drivesignal electrode 41 and the drive ground electrode 42, which will bedescribed later, are provided) to which an electric field for drivingthe e drive arms 25, 26 and 27. Further, the weight 222 is a portion onthe tip end side of the arm 221. Similarly, the weights 232, 242, 252,262, and 272 are portions on the tip end sides of the arms 231, 241,251, 261, and 271, respectively.

As illustrated in FIG. 3 , the weight 242 includes a first portion(centroid) 242 a on an extension line of the arm 241 and a pair ofsecond portions (flanks) 242 b and 242 c on both sides in the widthdirection of the first portion 242 a. As illustrated in FIG. 4 , athickness t2 of each of second portions 242 b and 242 c is thinner thana thickness t1 of the first portion 242 a. Here, a first principalsurface 2 a is flat (planar), whereas a second principal surface 2 b isprovided with steps 244 and 245 by the first portion 242 a and thesecond portions 242 b and 242 c. The steps 244 and 245 are configured toinclude inclined surfaces (chamfered), and the thickness of the weight242 gradually increases (inwardly) from the second portions 242 b and242 c side toward the first portion 242 a side. The second portions 242b and 242 c as described above can be formed by etching (anisotropicetching) the second principal surface 2 b of the weight 242 as describedlater.

As illustrated in FIG. 4 , the center of gravity G1 of such a weight 242is positioned closer to the first principal surface 2 a side of thefirst principal surface 2 a (lower surface) and the second principalsurface 2 b (upper surface) of the weight 242 that are in a front andback relationship with respect to the center C of the drive arm 24 inthe thickness direction. That is, the centers of gravity G1 of theweights 242, 252, 262, and 272 are (offset towards) at positions on thefirst principal surface 2 a side than to a center plane CP of the arms241, 251, 261, and 271, in the thickness direction whereas the centersof gravity G2 of the weight films 33, 34, 35, and 36 are (offsettowards) at positions on the second principal surface 2 b side than tothe center plane CP of the arms 241, 251, 261, and 271 in the thicknessdirection. By shifting the center of gravity G1 in the thicknessdirection with respect to the center C in this manner, it is possible tobalance with the weight film 33 having the center of gravity G2positioned on the side opposite to the center of gravity G1 of theweight 242 as described later. Similarly to the weight 242, the centersof gravity G1 of the weights 252, 262, and 272 are positioned closer toon the first principal surface 2 a side of the first principal surface 2a (lower surface) and the second principal surface 2 b (upper surface)that are in a front and back relationship of the weights 252 of each ofthe weights 252, 262, and 272 than the center C of the drive arms 25,26, and 27 in the thickness direction. Also, the centers of gravity ofthe weights 222 and 232 may also be positioned closer to on the firstprincipal surface side of the first principal surface (lower surface)and the second principal surface (upper surface) that are in the frontand back relationship of each of the weights 222 and 232 with respect toeach of the centers of the detection arms 22 and 23 in the thicknessdirection.

Here, “the central plane CP of the arm 241” in the thickness directionrefers to a plane which is orthogonal to the thickness direction (z-axisdirection) of the arm 241 and in which the distance between theoutermost portion in the thickness direction on the first principalsurface 2 a side of the arm 241 and the outermost portion in thethickness direction on the second principal surface 2 b side is equal.The center plane of the arms 251, 261, and 271 in the thicknessdirection is also defined in the same manner as the center plane CP ofthe arm 241 in the thickness direction. “The weight film 33” refers to alaminate (on the drive arm 24) having a larger mass per unit area thanthe electrode film 4 (drive signal electrode 41 and drive groundelectrode 42) of the arm 241. The weight films 34, 35, and 36 are alsodefined in the same manner as the weight film 33, respectively.

The depth d1 of the steps 244 and 245 of the second principal surface 2b, that is, the difference between the thickness t1 of the first portion242 a and the thickness t2 of the second portions 242 b and 242 c is notparticularly limited but is preferably equal to the depth d2 of thegroove 243 (see FIG. 5 ). With this configuration, the steps 244 and 245described above can be collectively formed with the grooves 243 byetching. The depth d1 of the step is preferably 0.1 times or more and0.5 times or less, more preferably 0.15 times or more and 0.4 times orless with respect to the thickness t1 of the weight 242.

The widths Wb and Wc of the second portions 242 b and 242 c may be equalto or different from each other, but it is preferable that the width Wcof the second portion 242 c (inboard flank) is larger than the width Wbof the second portion 242 b (outboard flank). In a case where thevibrator element 2 is formed by anisotropic etching of the Z-cut quartzcrystal plate, due to its anisotropy, an average thickness of the secondportion 242 b becomes thicker than the average thickness of the secondportion 242 c. For that reason, the mass of the second portion 242 b andthe mass of the second portion 242 c can be equalized by making thewidth Wc of the second portion 242 c larger than the width Wb of thesecond portion 242 b.

The widths Wb and Wc of the specific second portions 242 b and 242 c aredetermined according to the thickness, the area, and the like of theweight film 33 to be described later, respectively, and are notparticularly limited, but the widths Wb and We are about 0.3 times to0.8 times the width Wa of the first portion 242 a. The area of each ofthe second portions 242 b and 242 c in a plan view is not particularlylimited, but is, for example, about 0.1 times to 2 times the area of thefirst portion 242 a in a plan view.

The vibrator element 2 is configured by a Z-cut quartz crystal plate. Byconfiguring the vibrator element 2 with a quartz crystal (Z-cut quartzcrystal plate), it is possible to improve the vibration characteristics(especially, frequency-temperature characteristics) of the vibratorelement 2. Further, the vibrator element 2 can be formed with highdimensional accuracy by etching. The quartz crystal belongs to atrigonal system and has the X-axis, Y-axis, and Z-axis orthogonal toeach other as a crystal axis. The X-axis, the Y-axis, and the Z-axis arereferred to as an electric axis, a mechanical axis, and an optical axis,respectively. The Z-cut quartz crystal plate is a plate-like quartzcrystal substrate having a spread in the XY-plane defined by the Y-axis(mechanical axis) and the X-axis (electric axis) and having a thicknessin the Z-axis (optical axis) direction. Here, the X-axis of the quartzcrystal configuring the vibrator element 2 is parallel to the x-axis,the Y-axis is parallel to the y-axis, and the Z-axis is parallel to thez-axis.

In addition, the vibrator element 2 may be made of a piezoelectricmaterial other than quartz crystal. Examples of the piezoelectricmaterial other than quartz crystal include lithium tantalate, lithiumniobate, lithium borate, barium titanate, and the like. Depending on theconfiguration of the vibrator element 2, the vibrator element 2 may beconfigured by of a quartz crystal plate having a cut angle other thanthe Z-cut. Further, the vibrator element 2 may be made of a material (amaterial not having piezoelectricity) other than the piezoelectricmaterial, for example, silicon, and in this case, a piezoelectricelement (element having a structure in which a piezoelectric film madeof PZT or the like is sandwiched between a pair of electrodes) may bedisposed on each of the arms of the detection arms 22 and 23 and thedrive arms 24, 25, 26, and 27.

The electrode film 4 is provided on the surface of the vibrator element2 configured as described above. As illustrated in FIG. 2 , theelectrode film 4 includes drive signal electrodes 41, drive groundelectrodes 42, detection signal electrodes 43, detection groundelectrodes 44, and a plurality of terminals (not illustrated)electrically connected to these electrodes.

The drive signal electrodes 41 are electrodes for exciting drivevibration of the drive arms 24, 25, 26, and 27. As illustrated in FIG. 2, the drive signal electrodes 41 are provided on the upper and lowersurfaces of the arm 241 of the drive arm 24 and are provided on bothside surfaces of the arm 261 of the drive arm 26, respectively.Similarly, although not illustrated, the drive signal electrodes 41 areprovided on the upper and lower surfaces of the arm 251 of the drive arm25 and are provided on both side surfaces of the arm 271 of the drivearm 27, respectively.

On the other hand, each of the drive ground electrodes 42 has areference potential (for example, ground potential) with respect to eachof the drive signal electrodes 41. As illustrated in FIG. 2 , the driveground electrodes 42 are provided on both side surfaces of the arm 241of the drive arm 24 and are provided on upper and lower surfaces of thearm 261 of the drive arm 26, respectively. Similarly, although notillustrated, the drive ground electrodes 42 are provided on both sidesurfaces of the arm 251 of the drive arm 25 and are provided on upperand lower surfaces of the arm 271 of the drive arm 27, respectively.

The detection signal electrodes 43 are electrodes for detecting theelectrical charge generated by detection vibration of the detection arm22 when the detection vibration is excited. As illustrated in FIG. 2 ,the detection signal electrodes 43 are provided on the upper and lowersurfaces of the arm 221 of the detection arm 22, respectively.

On the other hand, each of the detection ground electrodes 44 has areference potential (ground potential, for example) with respect to eachof the detection signal electrodes 43. As illustrated in FIG. 2 , thedetection ground electrodes 44 are provided on both side surfaces of thearm 221 of the detection arm 22.

Although not illustrated, the detection signal electrodes for detectingthe electric charge of the detection arm 23 generated by the detectionvibration of the detection arm 23 when the detection vibration of thedetection arm 23 is excited are provided on the upper and lower surfacesof the arm 231 of the detection arm 23. Similarly, each of the detectionground electrodes of the detection arm 23 has a potential (for example,ground potential) serving as a reference with respect to each of thedetection signal electrodes of the detection arm 23, and are provided onboth side surfaces of the arm 231 of the detection arm 23. Vibrationdetection may be performed by a differential signal between thedetection signal electrodes 43 of the detection arm 22 and the detectionsignal electrodes of the detection arm 23.

As the constituent materials of the electrode film 4, although notparticularly limited, metallic materials, for example, gold (Au), goldalloy, platinum (Pt), aluminum (Al), aluminum alloy, silver (Ag), silveralloy, chromium (Cr), chromium alloy, copper (Cu), molybdenum (Mo),niobium (Nb), tungsten (W), iron (Fe), titanium (Ti), cobalt (Co), zinc(Zn), zirconium (Zr), or a transparent electrode material such as ITO orZnO can be used. Among the materials, it is preferable to use a metal(gold, gold alloy) or platinum mainly composed of gold. A layer of Ti,Cr, or the like may be provided as an underlayer having a function ofpreventing the electrode film 4 from peeling from the vibrator element 2between the electrode film 4 and the vibrator element 2.

The electrode film 4 has portions disposed on the weights 222, 232, 242,252, 262, and 272 of the vibrator element 2 described above. The weightfilm 3 is disposed on the weights 222, 232, 242, 252, 262, and 272 viathe portions, respectively. The electrode films 4 may not be disposeddirectly under the weight film 3.

As illustrated in FIG. 1 , the weight film 3 has a weight film 31disposed on the weight 222, a weight film 32 disposed on the weight 232,a weight film 33 disposed on the weight 242, a weight film 34 disposedon the weight 252, a weight film 35 disposed on the weight 262, and aweight film 36 disposed on the weight 272. The weight films 31 and 32are films which can be used for adjusting the resonance frequency of thedetection arms 22 and 23 by being removed by an appropriate amount bythe energy ray such as a laser. Further, the weight films 33, 34, 35,and 36 are films which can be used for adjusting the resonance frequencyof the drive arms 24, 25, 26, and 27 by being removed by an appropriateamount by the energy ray such as a laser.

The weight film 33 is disposed on the second principal surface 2 b (ofthe first principal surface 2 a (lower surface) and the second principalsurface 2 b (upper surface) that are in the front and back relationshipof the weight 242), and is not disposed on the first principal surface 2a. The weight film 33 is also not disposed on the side surfaces (rightand left side surfaces and front end surface) of the weight 242. In thepresent embodiment, the weight film 33 is provided over the entireregion in the width direction (x-axis direction) of the weight 242 butis excluded from a part on the base end side of the weight 242.Accordingly, the weight film 33 is disposed over the first portion 242 aand the second portions 242 b and 242 c of the weight 242.

As illustrated in FIG. 4 , the center of gravity G2 of such a weightfilm 33 is positioned closer to the second principal surface 2 b side(of the first principal surface 2 a (lower surface) and the secondprincipal surface 2 b (upper surface) that are in the front and backrelationship of the weight 242) with respect to the center C of thedrive arm 24 in the thickness direction. By shifting the center ofgravity G2 in the thickness direction with respect to the center C inthis manner, it is possible to balance with the weight 242 having thecenter of gravity G1 positioned on the side opposite to the center ofgravity G2 of the weight film 33 as described later. Similarly to theweight film 33, each of the centers of gravity of the weight films 34,35, and 36 is positioned closer to the second principal surface 2 b side(of the first principal surface 2 a (lower surface) and the secondprincipal surface 2 b (upper surface) that are in the front and backrelationship) of each of the weights 252, 262, and 272 with respect tothe center C of each of the drive arms 25, 26, and 27 in the thicknessdirection. In addition, the centers of gravity of the weight films 31and 32 are respectively positioned closer to the second principalsurface side (of the first principal surface (lower surface) and thesecond principal surface (upper surface) that are in a front and backrelationship) of each of the weights 222 and 232 with respect to thecenter of each of the detection arms 22 and 23 in the thicknessdirection.

The position, size, range, and the like of the weight films 31 to 36 arenot limited to the positions, sizes, ranges, and the like illustrated inthe drawings. For example, the weight film 3 may be disposed on thefirst principal surface 2 a and side surfaces of each of the weights222, 232, 242, 252, 262, and 272. In this case, with respect to theweight films 33, 34, 35, and 36 excluding the weight films 31, 32, thethickness, the disposition, and the like may be adjusted so that thecenters of gravity G2 of the weight films are positioned on the secondprincipal surface 2 b side. Further, the weight film 3 may be providedover the entire region in the length direction (y-axis direction) of theweights 222, 232, 242, 252, 262, and 272.

The constituent material of the weight film 3 is not particularlylimited, and, for example, metal, an inorganic compound, resin, or thelike can be used, but it is preferable to use metal or an inorganiccompound. Films of metal or the inorganic compound can be formed easilyand highly accurately by a vapor phase film disposition method. Theweight films 31 to 36 made of metal or inorganic compound can beefficiently and highly accurately removed by irradiation with energybeams. From the matters described above, the frequency adjustmentdescribed later becomes more efficient and highly accurate by formingthe weight film 3 with a metal or an inorganic compound.

Examples of such metals include nickel (Ni), gold (Au), gold alloy,platinum (Pt), aluminum (Al), aluminum alloy, silver (Ag), silver alloy,chromium (Cr), chromium alloy, copper (Cu), molybdenum (Mo), niobium(Nb), tungsten (W), iron (Fe), titanium (Ti), cobalt (Co), zinc (Zn),zirconium (Zr), and the like, and one kind or a combination of two ormore kinds of the metals can be used. Among these metals, Al, Cr, Fe,Ni, Cu, Ag, Au, Pt or an alloy containing at least one of these metalscan be used as the metal from the viewpoint that the weight film 3 canbe formed using the same material as the electrode film 4. Morespecifically, it is preferable that the weight film 3 has a structure inwhich an upper layer made of Au (gold) is laminated on an underlayermade of, for example, Cr (chromium). With this configuration, adhesionto the vibrator element 2 or the electrode film 4 formed by using quartzcrystal is excellent, and adjustment of the resonance frequency can beperformed with high accuracy and efficiency.

Examples of such inorganic compounds include oxide ceramics such asalumina (aluminum oxide), silica (silicon oxide), titania (titaniumoxide), zirconia, yttria, and calcium phosphate, nitride ceramics suchas silicon nitride, aluminum nitride, titanium nitride, and boronnitride, carbide-based ceramics such as graphite and tungsten carbide,and in addition, ferroelectric materials such as barium titanate,strontium titanate, PZT, PLZT, PLLZT, and the like. Among the materials,it is preferable to use an insulating material such as silicon oxide(SiO₂), titanium oxide (TiO₂), and aluminum oxide (Al₂O₃).

The thickness (average thickness) of the weight film 3 is notparticularly limited but is, for example, about 10 nm or more and 10000nm or less.

The vibration element 1 configured as described above detects an angularvelocity ω around the z-axis as follows. First, by applying a voltage(drive signal) between the drive signal electrode 41 and the driveground electrode 42, the drive arm 24 and the drive arm 26 subjected toflexural vibration (drive vibration) so that the drive arm 24 and thedrive arm 26 repeat approaching and separating from each other in thedirection indicated by the arrow a in FIG. 1 and the drive arm 25 andthe drive arm 27 are subjected to flexural vibration (drive vibration)so that the drive arm 25 and the drive arm 27 repeat approaching andseparating from each other in the same direction as the flexuralvibration. At this time, if an angular velocity is not applied to thevibration element 1, the drive arms 24 and 25 and the drive arms 26 and27 is subjected to plane-symmetric vibration with respect to theyz-plane passing through the center point (center of gravity G) andthus, the base main body 211, the connecting arms 212 and 213, and thedetection arms 22 and 23 hardly vibrate. At this time, as describedabove, since the centers of gravity G1 of the weights 242, 252, 262, and272 and the centers of gravity G2 of the weight films 33, 34, 35, and 36are positioned on opposite sides with respect to the center C of thedrive arms 24, 25, 26, and 27, vibration the drive arms 24, 25, 26, and27 in the out-of-plane direction of can be reduced.

When the angular velocity ω around the normal line passing through thecenter of gravity G of the vibration element 1 (that is, around thez-axis) is applied to the vibration element 1 in a state (drive mode)where the drive arms 24 to 27 are subjected to drive vibration, aCoriolis force acts on each of the drive arms 24 to 27. With thisconfiguration, the connecting arms 212 and 213 are subjected to flexuralvibration in the direction indicated by the arrow b in FIG. 1 , andalong with this, the flexural vibration (detection vibration) of thedetection arms 22 and 23 in the direction indicated by the arrow c inFIG. 1 is excited so as to cancel this flexural vibration. Electriccharges are generated between the detection signal electrodes 43 and thedetection ground electrodes 44 according to the detection vibration(detection mode) of the detection arms 22 and 23. Based on such electriccharges, the angular velocity ω applied to the vibration element 1 canbe obtained.

As described above, the vibration element 1 includes the base 21, thedrive arms 24, 25, 26, and 27 which are vibrating arms that extend fromthe base 21, have the arms 241, 251, 261, and 271 positioned closer tothe base 21 side and the weights 242, 252, 262, and 272 are at positionsmore on the tip end side than the arms 241, 251, 261, and 271, and theweight films 33, 34, 35, and 36 disposed on the weights 242, 252, 262,and 272. Here, each of the weights 242, 252, 262, and 272 has the firstprincipal surface 2 a and the second principal surface 2 b which are ina front and back relationship. The centers of gravity G1 of the weights242, 252, 262, and 272 are at positions more on the first principalsurface 2 a side relative to the center plane CP (plane passing throughthe center C of the drive arms 24, 25, 26, and 27 in the thicknessdirection and orthogonal to the z-axis) of the arms 241, 251, 261, and271 in the thickness direction. In contrast, the centers of gravity G2of the weight films 33, 34, 35, and 36 are at positions more on thesecond principal surface 2 b side relative to the center plane CP of thearms 241, 251, 261, and 271 in the thickness direction.

According to such a vibration element 1, the centers of gravity G1 ofthe weights 242, 252, 262, and 272 are at positions more on the firstprincipal surface 2 a side than the central surface CP of the arms 241,251, 261, and 271 in the thickness direction, whereas the centers ofgravity G2 of the weight films 33, 34, 35, and 36 are at positions moreon the second principal surface 2 b side than the central surface CP ofthe arms 241, 251, 261, and 271 in the thickness direction. Thus, thecenter of gravity of the entire structure composed of the weights 242,252, 262, and 272 and the weight films 33, 34, 35, and 36 can be broughtclose to the center plane CP (center C of the drive arms 24, 25, 26, and27). For that reason, it is possible to reduce unnecessary vibrations(vibration in the thickness direction) of the drive arms 24, 25, 26, and27, and as a result, it is possible to reduce noise vibration to theoutside of the vibration element 1. Although a manufacturing method willbe described later, since it is sufficient to dispose the weight films33, 34, 35, and 36 only on one side (specifically, on the secondprincipal surface 2 b side) of the weights 242, 252, 262, and 272, themanufacturing process of the vibration element 1 can be simplified, apart of the weight films 33, 34, 35, and 36 can be removed by an energyray such as a laser, and a splash (dross) generated when adjusting theresonance frequency of the vibrating arm can be reduced.

The center of gravity G1 of each of the weights 242, 252, 262, and 272is positioned on the first principal surface 2 a side (on the same side)and the center of gravity G2 of each of the weight films 33, 34, 35, 36is positioned on the second principal surface 2 b side (on the sameside), and it is easy to form the weights 242, 252, 262, and 272 and theweight films 33, 34, 35, and 36. One of the drive arms 24, 25, 26, and27 corresponds to a “first vibrating arm”, and another one correspondsto a “second vibrating arm”. The first vibrating arm includes one of thearms 241, 251, 261, and 271 as a first arm and includes a weight, whichis connected to the first arm, of the weights 242, 252, 262, and 272 asa first weight. The second vibrating arm includes a weight differentfrom the first weight of the arms 241, 251, 261, and 271 as a secondarm, and includes a weight, which is connected to the second arm, of theweights 242, 252, 262, and 272 as a second weight. One of the weightfilms 33, 34, 35, and 36 as the first weight film is disposed on thefirst weight, and one of the weight films 33, 34, 35, and 36 as thesecond weight film is disposed on the second weight.

Here, it is preferable that each of the arms 241, 251, 261, and 271 hasa shape that is plane-symmetric with respect to the center plane CP inthe thickness direction. With this configuration, it is possible toreduce vibration in the thickness direction due to the shape of thedrive arms 24, 25, 26, and 27.

The vibration element 1 of this embodiment includes drive arms 24, 25,26, and 27 that are subjected to drive vibration and the detection arms22 and 23 that deform in accordance with an inertial force, and the base21 includes the base main body 211 and the connecting arms 212 and 213which are connectors extending from the base main body 211. The drivearms 24, 25, 26, and 27 are vibrating arms and extend from theconnecting arms 212 and 213, and the detection arms 22 and 23 extendfrom the base main body 211. With this configuration, thecharacteristics of a so-called double T-type vibration element 1 can beimproved.

The width W of each of the weights 242, 252, 262, and 272 is larger thanthe width WO of each of the arms 241, 251, 261, and 271 in a plan viewfrom the thickness direction of the weight 242. With this configuration,it is possible to increase each of the areas of the weights 242, 252,262, and 272 in which the weight films 33, 34, 35, and 36 can berespectively formed. Further, the lengths of the drive arms 24, 25, 26,and 27 can be shortened, and as a result, miniaturization of thevibration element 1 can be achieved.

The weight 242 has the first portion 242 a and the second portions 242 band 242 c that are thinner than that of the first portion 242 a. Thesecond principal surface 2 b has the stepped steps 244 and 245 by thefirst portion 242 a and the second portions 242 b and 242 c. With thisconfiguration, it is possible to position the center of gravity G1 ofthe weight 242 closer to the first principal surface 2 a side than tothe center plane CP of the arm 241 in the thickness direction with arelatively simple configuration. The weights 252, 262, and 272 are alsoconfigured in the same manner as the weight 242, and exhibit the sameeffect. Here, the “step 244” has a shape in which the average distancefrom the center plane to the second principal surface 2 b of the weight242 in the first portion 242 a in the thickness direction is larger thanthe average distance from the center plane to the second principalsurface 2 b of the weight 242 in the second portion 242 b in thethickness direction. “The center plane of the weight 242” in thethickness direction refers to a plane which is orthogonal to thethickness direction of the weight 242 and in which the distance betweenthe outermost portion in the thickness direction on the first principalsurface 2 a side of the weight 242 and the outermost portion in thethickness direction on the second principal surface 2 b side of theweight 242 are equal. The thickness direction of the weight 242 and thethickness direction of the arm 241 are the same. In the drawing, thecenter plane of the weight 242 in the thickness direction and the centerplane CP of the arm 241 in the thickness direction are on the sameplane. The step 245 is also defined in the same manner as the step 244.

The steps 244 and 245 provided on the second principal surface 2 bdescribed above contain inclined surfaces, and the weight 242 has aportion where the thickness gradually decreases between the firstportion 242 a and the second portions 242 b and 242 c in a plan viewfrom the thickness direction of the weight 242. With this configuration,the weight film 33 can be easily formed continuously over the firstportion 242 a and the second portions 242 b and 242 c. It is possible toreduce the occurrence of cracks in the weight film 33 due to the steps244 and 245 between the first portion 242 a and the second portions 242b and 242 c. The weights 252, 262, and 272 are also configured in thesame manner as the weight 242, and exhibit the same effect.

In this embodiment, the second portions 242 b and 242 c are disposed onboth sides in the width direction of the drive arm 24 (vibrating arm)with respect to the first portion 242 a. With this configuration, it ispossible to reduce the mass of both end portions in the width directionof the weight 242 and to reduce a torsional moment of the drive arm 24.The weights 252, 262, and 272 are also configured in the same manner asthe weight 242, and exhibit the same effect.

The first principal surface 2 a of the weight 242 is a flat surface.With this configuration, it is not necessary to process the firstprincipal surface 2 a side of the weight 242 in order to provide thefirst portion 242 a and the second portions 242 b and 242 c in theweight 242, and as a result, the manufacturing process of the vibrationelement 1 can be simplified. The weights 252, 262, and 272 are alsoconfigured in the same manner as the weight 242, and exhibit the sameeffect. Although the first principal surface 2 a may have a step likethe second principal surface 2 b, since the position of the center ofgravity G1 is set as described above, it is preferable that the depth ofthe step of the first principal surface 2 a is shallower than the depthof the step of the second principal surface 2 b.

The weight film 33 is disposed on the first portion 242 a and the secondportions 242 b and 242 c. With this configuration, the mass of theweight film 33 can be increased. Further, forming of the weight film 33can be simplified. The weight films 34, 35, and 36 are also configuredin the same manner as the weight film 33, and exhibit the same effect.The weight film 33 may be provided on only one of the first portion 242a and the second portions 242 b and 242 c as long as the center ofgravity G2 is positioned as described above. Here, in the case where theweight film 33 is provided only on the first portion 242 a, there is anadvantage that mass balance in the width direction of the drive arm 24can be easily obtained as compared with the case where the weight film33 is provided only on the second portions 242 b and 242 c.

In addition, although the thickness of the weight film 33 is uniform inthe drawing, the weight film 33 may have a plurality of portions havingdifferent thicknesses from each other. That is, the weight film 33 mayinclude a first weight film and a second weight film having a thicknessthinner than that of the first weight film. In this case, it is possibleto easily perform fine adjustment and coarse adjustment when adjustingthe resonance frequency of the drive arm 24 by removing a part of theweight film 33 with an energy ray such as a laser. Here, the firstweight film having a thick thickness has large mass per unit area and issuitable for coarse adjustment (rough adjustment) of the resonancefrequency of the drive arm 24. On the other hand, the second weight filmhaving a small thickness has small mass per unit area and is suitablefor fine adjustment (minute adjustment) of the resonance frequency ofthe drive arm 24. Further, the weight films 34, 35, and 36 also exhibitthe same effect by being configured in the same manner as the weightfilm 33.

In this embodiment, although description is made on a case where withrespect to the drive arms 24, 25, 26, and 27, the center of gravity ofthe entire structure composed of the weights 242, 252, 262, and 272 andthe weight films 33, 34, 35, and 36 is brought close to the center C ofeach of the drive arms 24, 25, 26, and 27, the detection arms 22 and 23may also be configured similarly to the drive arms 24, 25, 26, and 27.In this case, the center plane of the arms 221 and 231 in the thicknessdirection is defined in the same manner as the center plane of the arm241 in the thickness direction. The weight films 31 and 32 are definedin the same manner as the weight film 33, respectively.

Manufacturing Method of Vibration Element

In the following, a manufacturing method of the vibration elementaccording to the invention will be described by taking a case ofmanufacturing the vibration element 1 described above as an example.

FIG. 6 is a flowchart illustrating an example of a manufacturing methodof the vibration element. As illustrated in FIG. 6 , the manufacturingmethod of the vibration element 1 includes a vibrator element formingstep S10, an electrode forming step S20, a weight film forming step S30,and a frequency adjusting step S40. Each step will be described insequence below.

Vibrator Element Forming Step S10

FIG. 7 is a cross-sectional view illustrating a sub-step of preparing asubstrate in a vibrator element forming step. FIG. 8 is across-sectional view illustrating a sub-step of forming acorrosion-resistant film and a resist film in the vibrator elementforming step. FIG. 9 is a cross-sectional view illustrating a sub-stepof forming an outer shape of the vibrator element in the vibratorelement forming step. FIG. 10 is a cross-sectional view illustrating asub-step of removing a part of the corrosion-resistant film in thevibrator element forming step. FIG. 11 is a cross-sectional viewillustrating a sub-step of forming a groove portion in the vibratorelement forming step. FIG. 12 is a cross-sectional view illustrating asub-step of removing the corrosion-resistant film and the resist film inthe vibrator element forming step. FIGS. 7 to 12 illustratecross-sections corresponding to FIG. 5 .

First, the vibrator element 2 is formed. Specifically, for example,first, as illustrated in FIG. 7 , a quartz crystal substrate 20 havingthe first principal surface 2 a and the second principal surface 2 b isprepared. Then, as illustrated in FIG. 8 , corrosion-resistant films 51and 52 and resist films 53 and 54 are sequentially formed on bothsurfaces of the quartz crystal substrate 20. Here, each of thecorrosion-resistant films 51 and 52 is a laminated film in which, forexample, chromium and gold are laminated in this order by vapordeposition method, sputtering method, or the like, has resistance to anetching solution used for the sub-step of forming the outer shape andthe sub-step of forming the groove which will be described later, and ispatterned according to a shape (outer shape) of the vibrator element 2in a plan view. Each of the resist films 53 and 54 is a film made of aresist material, has resistance to an etching solution used for thesub-step of forming the outer shape and the sub-step of forming thegroove which will be described later, and is patterned by beingsubjected to exposure and development according to the shape in a planview of the groove 243, the second portions 242 b and 242 c and the likeas well as the shape in a plan view (external shape) of the vibratorelement 2.

Next, as illustrated in FIG. 9 , the quartz crystal substrate 20 isetched using the corrosion-resistant films 51 and 52 and the resistantfilms 53 and 54 as a mask to obtain a quartz crystal substrate 20Ahaving the same outer shape as the vibrator element 2 (outer shapeforming sub-step). Thereafter, as illustrated in FIG. 10 , thecorrosion-resistant film 52 is etched by using the resist film 54 as amask to obtain a corrosion-resistant film 52A. As illustrated in FIG. 11, the quartz crystal substrate 20A is etched using thecorrosion-resistant films 51 and 52A and the resist films 53 and 54 as amask, and as illustrated in FIG. 12 , the corrosion-resistant films 51and 52A and the resist films 53 and 54 are removed by etching or thelike to obtain the vibrator element 2 (groove forming sub-step).

Here, the vibrator element 2 may be in a state (hereinafter, alsoreferred to as “wafer state”) of being connected to another part of thequartz crystal substrate 20A. In this wafer state, for example, thevibrator element 2 is connected to the other part of the quartz crystalsubstrate 20A through a folding portion of which at least one of thewidth and thickness is small and weakly formed. Further, in the waferstate, it is possible to collectively form a plurality of vibrationelements 1 on the quartz crystal substrate 20A.

Electrode Forming Step S20

FIG. 13 is a cross-sectional view illustrating an electrode formingstep.

As illustrated in FIG. 13 , the electrode film 4 is formed. Morespecifically, a metal film is uniformly formed on the surface of thevibrator element 2, for example, by sputtering or the like. Then, aphotoresist is applied, exposed, and developed to obtain a resist mask,and then the metal film in the part exposed from the resist mask isremoved using an etching solution. With this configuration, theelectrode film 4 is formed.

Weight Film Forming Step S30

FIG. 14 is a cross-sectional view illustrating a weight film formingstep.

As illustrated in FIG. 14 , the weight film 3 is formed by maskevaporation or the like.

Frequency Adjusting Step S40

FIG. 15 is a cross-sectional view illustrating a frequency adjustingstep.

As illustrated in FIG. 15 , a part of the weight film 3 is removed bythe energy ray LL as desired. More specifically, as desired, a part ofthe weight films 33 to 36 is removed so that the resonance frequenciesof the drive arms 24 to 27 are equal to each other, and the frequencies(resonance frequencies of the drive arms 24 to 27) of drive vibrationsare adjusted. Further, as desired, a part of the weight films 31 and 32is removed, and the frequencies (resonance frequency of the detectionarms 22 and 23) of detection vibrations are adjusted.

As the energy ray LL, for example, a pulsed laser such as YAG, YVO₄,excimer laser or the like, a continuous oscillation laser such as acarbon dioxide gas laser, focused ion beam (FIB), ion beam figuring(IBF), or the like can be used.

Such a frequency adjusting step S40 may be performed in the wafer stateor in a state of being mounted on a package 11 which will be describedlater. Further, the frequency adjusting step S40 may be performed in aplurality of times. For example, coarse adjustment may be performed as afirst adjustment in a wafer state and fine adjustment may be performedas a second adjustment in a state of being mounted on the package 11.

As described above, the manufacturing method of the vibration element 1includes the step (vibrator element forming step S10) of forming thedrive arm 24 (vibrating arm) which extends from the base 21, has thebase 21, the first principal surface 2 a and the second principalsurface 2 b which are in a front and back relationship with respect tothe thickness direction of the vibration element 1, and of which thecenter of gravity G1 is positioned closer to the first principal surface2 a side than to the center plane in the thickness direction, the step(weight film forming step S30) of forming the weight film 33 on thedrive arm 24, of which the center of gravity G2 is positioned closer tothe second principal surface 2 b side than to the center plane of thedrive arm in the thickness direction, and a step (frequency adjustingstep S40) of adjusting the resonance frequency of the drive arm 24 byadjusting the mass of the weight film 33. According to such amanufacturing method of the vibration element 1, the characteristics ofthe obtained vibration element 1 can be improved. “The center plane ofthe drive arm 24” in the thickness direction refers to a plane which isorthogonal to the thickness direction of the drive arm 24 and in whichthe distance between the outermost portion in the thickness direction onthe first principal surface 2 a side of the drive arm 24 and theoutermost portion in the thickness direction on the second principalsurface 2 b side of the drive arm 24 are equal. In this embodiment,although description is made by taking the case where the frequency isadjusted by reducing the mass of the weight film 33 by removing a partof the weight film 33 by the energy ray LL as an example, the frequencymay be adjusted by increasing the mass of the weight film 33 by forminga film on the weight film 33 by a film formation method such assputtering. The same applies to the resonance frequencies of the otherdrive arms 25 to 27 and the detection arms 22 and 23.

Second Embodiment

FIG. 16 is an enlarged plan view illustrating a weight and a weight filmof a vibrating arm (drive arm) of a vibration element according to asecond embodiment of the invention. FIG. 17 is a cross-sectional viewtaken along line C-C in FIG. 16 .

In the following, the second embodiment will be described, but thedifferences from the embodiment described above will be mainlydescribed, and description of similar matters will be omitted. In FIG.16 and FIG. 17 , the same reference numerals are given to the samecomponents as in the embodiment described above. In the followingdescription, one drive arm will be representatively described, but thesame applies to the other drive arms.

This embodiment is the same as the first embodiment described aboveexcept that the configuration (shape) of the weight is different.

As illustrated in FIG. 16 , a weight 242A of a drive arm 24A of avibration element 1A according to this embodiment includes a firstportion 242 d connected to the arm 241 and a second portion 242 edisposed on the side opposite to the arm 241 with respect to the firstportion 242 d. As illustrated in FIG. 17 , the thickness t2 of thesecond portion 242 e is thinner than the thickness t1 of the firstportion 242 d. Here, the weight film 33 is disposed over the firstportion 242 d and the second portion 242 e.

According to this embodiment as described above, similarly as in thefirst embodiment, the vibrating characteristics can be improved.

In this embodiment, the second portion 242 e is disposed on the sideopposite to the base 21 with respect to the first portion 242 d. Withthis configuration, since the second portion 242 e is positioned at thetip end portion of the drive arm 24A having a large mass effect, thearea of the second portion 242 e in a plan view can be reduced. Further,there is also an advantage that weight balance of the weight 242A in thewidth direction is difficult to collapse.

Third Embodiment

FIG. 18 is an enlarged plan view illustrating a weight and a weight filmof a vibrating arm (drive arm) of a vibration element according to thethird embodiment of the invention.

Hereinafter, a third embodiment will be described, but differences fromthe embodiments described above will be mainly described, anddescription of similar matters will be omitted. In FIG. 18 , the samereference numerals are given to the same configurations as those in theembodiment described above. In the following description, one drive armwill be representatively described, but the same applies to the otherdrive arms.

This embodiment is the same as the first embodiment described aboveexcept that the configuration (shape) of the weight is different.

A weight 242B of a drive arm 24B of a vibration element 1B of thisembodiment is formed by combining the first embodiment and the secondembodiment described above. That is, as illustrated in FIG. 18 , theweight 242B includes a first portion 242 f connected to the arm 241 anda second portion 242 g on both sides and the tip side in the widthdirection of the first portion 242 f. The thickness of the secondportion 242 g is thinner than the thickness of the first portion 242 f.Here, the weight film 33 is disposed over the first portion 242 f andthe second portion 242 g.

According to this embodiment as described above, similarly as in thefirst embodiment, the vibrating characteristics can be improved.

Fourth Embodiment

FIG. 19 is an enlarged plan view illustrating a weight and a weight filmof a vibrating arm (drive arm) of a vibration element according to afourth embodiment of the invention. FIG. 20 is a cross-sectional viewtaken along line B-B in FIG. 19 .

In the following, a fourth embodiment will be described, but thedifferences from the embodiments described above will be mainlydescribed, and description of similar matters will be omitted. In FIG.19 and FIG. 20 , the same reference numerals are given to the samecomponents as in the embodiment described above. In the followingdescription, one drive arm will be representatively described, but thesame applies to the other drive arms.

This embodiment is the same as the first embodiment described aboveexcept that the configuration (shape) of the weight is different.

As illustrated in FIG. 19 , a weight 242C of a drive arm 24C included ina vibration element 1C according to this embodiment includes aframe-shaped first portion 242 i connected to the arm 241 and a secondportion 242 h positioned inside the first portion 242 i. As illustratedin FIG. 20 , the thickness t2 of the second portion 242 h is thinnerthan the thickness t1 of the first portion 242 i. Here, the weight film33 is disposed over the first portion 242 i and the second portion 242 hin the width direction of the weight 242C.

According to this embodiment as described above, similarly as in thefirst embodiment, the vibrating characteristics can be improved.

Further, in this embodiment, the first portion 242 i surrounds thesecond portion 242 h in a plan view from the thickness direction of theweight 242C. Such a second portion 242 h is provided by forming a recess247. The recess 247 can be formed by etching similarly to the groove 243described above. For that reason, designing of the second portion 242 hbecomes easy.

Fifth Embodiment

FIG. 21 is a plan view illustrating a vibration element according to afifth embodiment of the invention.

In the following, a fifth embodiment will be described, but thedifferences from the embodiments described above will be mainlydescribed, and description of the same matters will be omitted.

This embodiment is the same as the first embodiment described aboveexcept that the invention is applied to a so-called H-type vibrationelement.

A vibration element 1D illustrated in FIG. 21 is a sensor element thatdetects an angular velocity around the y-axis. The vibration element 1Dincludes a vibrator element 2D, and an electrode film (not illustrated)and a weight film 3D provided on the vibrator element 2D.

The vibrator element 2D includes a base 21D, a pair of drive arms 24Dand 25D, and a pair of detection arms 22D and 23D. These are integrallyformed, and are formed by using a Z-cut quartz crystal plate. Thecorrespondence relationship between the crystal axis of the quartzcrystal and the x-axis, the y-axis, and the z-axis is similar to that ofthe first embodiment described above.

The base 21D is supported by a package 11 which will be described later.

The drive arms 24D and 25D extend from the base 21D in the y-axisdirection (+y-direction), respectively. The drive arms 24D and 25D areconfigured in the same manner as the drive arms of any one of the firstto fourth embodiments described above. Similarly to the drive arms 24 to27 of the first embodiment described above, although not illustrated, apair of drive electrodes (drive signal electrodes and drive groundelectrodes) for bending the drive arms 24D and 25D to vibrate in thex-axis direction by energization are provided on the drive arms 24D and25D, respectively. The pair of drive electrodes are electricallyconnected to terminals (not illustrated) on the base 21D via wirings(not illustrated).

The detection arms 22D and 23D extend from the base 21D in the y-axisdirection (−y direction), respectively. Although not illustrated, a pairof detection electrodes (a detection signal electrode and a detectionground electrode) for detecting electric charges generated with flexuralg vibration in the z-axis direction of the detection arms 22D and 23Dare provided on the detection arms 22D and 23D, respectively. The pairof detection electrodes are electrically connected to terminals (notillustrated) on the base 21D via wirings (not illustrated).

The weight film 3D includes weight films 31D and 32D disposed at the tipend portion (weight) of the detection arms 22D and 23D and weight films33D and 34D disposed on the tip end portion (weight) of the drive arms24D and 25D.

In the vibration element 1D configured as described above, a drivesignal is applied between a pair of drive electrodes, so that the drivearm 24D and the drive arm 25D are subjected to flexural vibration (drivevibration) so as to repeat approaching and separating from each other asindicated by arrows A1 and A2 in FIG. 21 .

When the angular velocity ω around the y-axis is applied to thevibration element 1D in a state where the drive arms 24D and 25D aresubjected to drive vibration, the drive arms 24D and 25D vibrate inopposite directions in the z-axis direction, as indicated by arrows B1and B2 in FIG. 21 , due to the Coriolis force. Along with this, thedetection arms 22D and 23D are subjected to flexural vibration(detection vibration) on opposite sides in the z-axis direction asindicated by arrows C1 and C2 in FIG. 21 .

The electric charge generated between the pair of detection electrodesby such flexural vibration of the detection arms 22D and 23D is outputfrom the pair of detection electrodes. Based on such electric charge,the angular velocity Ct) applied to the vibration element 1D can beobtained.

According to this embodiment as described above, similarly as in thefirst embodiment, the characteristics such as reliability can beimproved.

Here, the vibration element 1D according to this embodiment includes thedrive arms 24D and 25D which extend from the base 21D and are subjectedto drive vibration and detection arms 22D and 23D which extend from thebase 21D in the direction opposite to the drive arms 24D and 25D anddeform corresponding to the inertial force, and the drive arms 24D and25D are vibrating arms. With this configuration, the characteristics ofa so-called H-type vibration element 1D can be improved.

Sixth Embodiment

FIG. 22 is a plan view illustrating a vibration element according to asixth embodiment of the invention.

In the following, a sixth embodiment will be described, but differencesfrom the embodiments described above will be mainly described, anddescription of similar matters will be omitted.

This embodiment is the same as the first embodiment described aboveexcept that the invention is applied to a so-called two-legged tuningfork type vibration element.

A vibration element 1E illustrated in FIG. 22 is a sensor element thatdetects an angular velocity around the y-axis. The vibration element 1Eincludes a vibrator element 2E, an electrode film (not illustrated) andweight films 33E and 34E provided on the vibrator element 2E.

The vibrator element 2E includes a base 21E and a pair of vibrating arms24E and 25E, which are integrally formed, and are formed using a Z-cutquartz crystal plate. The correspondence relationship between thecrystal axis of the quartz crystal and the x-axis, the y-axis, and thez-axis is similar to that of the first embodiment described above.

The base 21E includes a first base 214 to which the vibrating arms 24Eand 25E are connected, a second base 216 disposed on the opposite sideof the vibrating arms 24E and 25E with respect to the first base 214,and a connector 215 connecting the first base 214 and the second base216. The connector 215 is positioned between the first base 214 and thesecond base 216, and has a width (length in the x-axis direction)smaller than that of the first base 214. With this configuration, it ispossible to reduce vibration leakage while reducing the length of thebase 21E along the y-axis direction. Here, the second base 216 issupported by, for example, a package 11 which will be described later.

The vibrating arms 24E and 25E respectively extend in the y-axisdirection (+y-direction) from the base 21E. The vibrating arms 24E and25E are configured similarly to the drive arms of any one of the firstto fourth embodiments described above. Similarly to the drive arms 24 to27 of the first embodiment described above, although not illustrated, apair of drive electrodes (drive signal electrodes and drive groundelectrodes) for bending the vibrating arms 24E and 25E to vibrate in thex-axis direction by energization are provided on the vibrating arms 24Eand 25E, respectively. The pair of drive electrodes are electricallyconnected to terminals (not illustrated) on the base 21E via wirings(not illustrated).

Although not illustrated, in addition to the pair of drive electrodesdescribed above, a pair of detection electrodes (a detection signalelectrode and a detection ground electrode) for detecting electriccharges generated with flexural g vibration in the z-axis direction ofthe vibrating arms 24E and 25E are provided on the vibrating arms 24Eand 25E, respectively. The pair of detection electrodes are electricallyconnected to terminals (not illustrated) on the base 21E via wirings(not illustrated).

The weight films 33E and 34E are disposed on the tip end portions(weights) of the vibrating arms 24E and 25E. In the vibration element 1Econfigured as described above, a drive signal is applied between a pairof drive electrodes, so that the vibrating arm 24E and the vibrating arm25E are subjected to flexural g vibration (drive vibration) so as torepeat approaching and separating from each other.

When the angular velocity ω around the y-axis is applied to thevibration element 1E in a state where the vibrating arms 24E and 25E aresubjected to drive vibration, vibrations bending in opposite directionsin the z-axis direction are excited by the Coriolis force to thevibrating arms 24E and 25E. The electric charge generated between thepair of detection electrodes due to the vibration excited in this manneris output from the pair of detection electrodes. Based on such electriccharge, the angular velocity ω applied to the vibration element 1E canbe obtained.

According to this embodiment as described above, as in the firstembodiment, the vibrating characteristics can be improved.

2. Physical Quantity Sensor

FIG. 23 is a cross-sectional view illustrating a physical quantitysensor according to an embodiment of the invention.

A physical quantity sensor 10 illustrated in FIG. 23 is a vibration gyrosensor that detects an angular velocity around the x-axis, the y-axis,or the z-axis. This physical quantity sensor 10 includes a vibrationelement 1 (or 1A, 1B, 1C, 1D, 1E), a support member 12, a circuitelement 13 (integrated circuit chip), and a package 11 that accommodatesthese constitutional elements.

The package 11 includes a box-like base 111 having a recess foraccommodating the vibration element 1 and a plate-like lid 112 joined tothe base 111 via a joining member 113 so as to close an opening of therecess of the base 111. Inside of the package 11 may be in adepressurized (vacuum) state or may be enclosed with inert gas such asnitrogen, helium, argon or the like.

The recess of the base 111 has an upper stage surface positioned on theopening side, a lower stage surface positioned on the bottom side, and amiddle stage surface positioned between the upper and lower stagesurfaces. The constituent material of the base 111 is not particularlylimited, but various ceramics such as aluminum oxide and various glassmaterials can be used. The constituent material of a lid 112 is notparticularly limited, but it may be a member having a coefficient oflinear expansion close to that of the constituent material of the base111. For example, in a case where the constituent material of the base111 is ceramics as described above, it is preferable to use an alloysuch as kovar. In this embodiment, a seam ring is used as the joiningmember 113, but the joining member 113 may be configured by using, forexample, low melting point glass, an adhesive, or the like.

A plurality of connection terminals 14 and 15 are provided on the upperstage surface and the middle stage surface of the recess of the base111, respectively. A part of the plurality of connection terminals 15provided on the middle stage surface is electrically connected to aterminal 16 provided on the bottom surface of the base 111 via a wiringlayer (not illustrated) provided on the base 111, and the remaining partis electrically connected to the plurality of connection terminals 14provided on the upper stage via wirings (not illustrated). Theseconnection terminals 14 and 15 are not particularly limited as long asthey have conductivity, but are constituted by a metallic coating filmobtained by laminating films of Ni (nickel), Au (gold), Ag (silver), Cu(copper), or the like on a metallization layer (underlayer) of Cr(chromium), W (tungsten) or the like.

The circuit element 13 is fixed to the lower stage surface of the recessof the base 111 with an adhesive 19 or the like. As the adhesive 19, forexample, an epoxy-based, silicone-based, or polyimide-based adhesive canbe used. The circuit element 13 includes a plurality of terminals (notillustrated), and these terminals are electrically connected to therespective connection terminals 15 provided on the middle stage surfacedescribed above by conductive wires. This circuit element 13 includes adrive circuit for allowing the vibration element 1 to be subjected todrive vibration and a detection circuit for detecting the detectionvibration occurring in the vibration element 1 when an angular velocityis applied.

The support member 12 is connected to the plurality of connectionterminals 14 provided on the upper stage surface of the recess of thebase 111 via a conductive adhesive 17. The support member 12 includes awiring pattern 122 connected to the conductive adhesive 17 and a supportsubstrate 121 supporting the wiring pattern 122. As the conductiveadhesive 17, for example, a conductive adhesive such as an epoxy-basedadhesive, a silicone-based adhesive, a polyimide-based adhesive or thelike mixed with a conductive substance such as a metal filler can beused.

The support substrate 121 has an opening at the center portion, and aplurality of elongated leads included in the wiring pattern 122 extendin the opening. The vibration element 1 is connected to the tip endportions of these leads via conductive bumps 123.

In this embodiment, the circuit element 13 is provided inside thepackage 11, but the circuit element 13 may be provided outside thepackage 11.

As described above, the physical quantity sensor 10 includes thevibration element 1 (or 1A, 1B, 1C, 1D, 1E) and the package 11accommodating the vibration element 1 (or 1A, 1 B, 1C, 1D, 1E).According to such a physical quantity sensor 10, it is possible toimprove the sensor characteristics (for example, detection accuracy) ofthe physical quantity sensor 10 by utilizing the excellentcharacteristics of the vibration element 1 (or 1A, 1B, 1C, 1D, 1E).

3. Inertial Measurement Device

FIG. 24 is an exploded perspective view illustrating an embodiment ofthe inertial measurement device according to the invention. FIG. 25 is aperspective view of a substrate included in the inertial measurementdevice illustrated in FIG. 24 .

An inertial measurement device (which corresponds to inertialmeasurement unit (IMU)) 2000 illustrated in FIG. 24 is a so-calledsix-axis motion sensor, is used by being attached to a vehicle(measurement target) such as an automobile, a robot, and detects anattitude and behavior (inertial momentum) of the vehicle detected.

The inertial measurement device 2000 includes an outer case 2100, ajoining member 2200, and a sensor module 2300. The sensor module 2300 isengaged (inserted) in the outer case 2100 in a state where the joiningmember 2200 is interposed.

The outer case 2100 has a box-like shape, and two corner portions atdiagonal corners of the outer case 2100 are provided with screw holes2110 for screwing the measurement target.

The sensor module 2300 includes an inner case 2310 and a substrate 2320.The sensor module 2300 is accommodated inside the outer case 2100 in astate where the inner case 2310 supports the substrate 2320. Here, theinner case 2310 is joined to the outer case 2100 with an adhesive or thelike via the joining member 2200 (for example, a rubber packing). Theinner case 2310 has a recess 2311 functioning as a storage space forcomponents to be mounted on the substrate 2320 and an opening 2312 forexposing the connector 2330 provided on the substrate 2320 to theoutside. The substrate 2320 is, for example, a multilayer wiring board,and is joined to the inner case 2310 with an adhesive or the like.

As illustrated in FIG. 25 , a connector 2330, angular velocity sensors2340X, 2340Y, and 2340Z, an acceleration sensor 2350, and a control IC2360 are mounted on the substrate 2320.

The connector 2330 is electrically connected to an external device (notillustrated), and is used to transmit and receive electric signals suchas electric power and measurement data between the external device andthe inertial measurement device 2000.

The angular velocity sensor 2340X detects the angular velocity aroundthe X-axis, the angular velocity sensor 2340Y detects the angularvelocity around the Y-axis, and the angular velocity sensor 2340Zdetects the angular velocity around the Z-axis. Here, each of theangular velocity sensors 2340X, 2340Y, and 2340Z is the physicalquantity sensor 10 described above. Further, the acceleration sensor2350 is, for example, an acceleration sensor formed by using the MEMStechnology and detects acceleration in each of the X-axis, Y-axis, andZ-axis directions.

The control IC 2360 is a micro controller unit (MCU), incorporates astorage unit including a nonvolatile memory, an A/D converter, and thelike, and controls each portion of the inertial measurement device 2000.Here, the storage unit stores a program that defines the order andcontents for detecting acceleration and angular velocity, a program thatdigitizes detection data to be incorporated into packet data,accompanying data, and the like.

As described above, the inertial measurement device 2000 includes thephysical quantity sensor 10 and the control IC 2360 which is a circuitelectrically connected to the physical quantity sensor 10. According tosuch an inertial measurement device 2000, it is possible to improvecharacteristics (for example, measurement accuracy) of the inertialmeasurement device 2000 by using excellent sensor characteristics of thephysical quantity sensor 10.

4. Electronic Apparatus

FIG. 26 is a perspective view illustrating an embodiment (mobile type(or notebook type) personal computer) of an electronic apparatusaccording to the invention.

In FIG. 26 , a personal computer 1100 is constituted by a main body 1104provided with a keyboard 1102 and a display unit 1106 provided with adisplay part 1108, and the display unit 1106 is rotatably supported tothe main body 1104 via a hinge structure. In such a personal computer1100, an inertial measurement device 2000 including the vibrationelement 1 (or 1A, 1B, 1C, 1D, 1E) described above is incorporated.

FIG. 27 is a plan view illustrating an embodiment (mobile phone) of theelectronic apparatus according to the invention. In FIG. 27 , a mobilephone 1200 includes an antenna (not illustrated), a plurality ofoperation buttons 1202, an earpiece 1204, and a mouthpiece 1206, and adisplay unit 1208 is disposed between the operation button 1202 and theearpiece 1204. In such a mobile phone 1200 the inertial measurementdevice 2000 including the vibration element 1 (or 1A, 1B, 1C, 1D, 1E)described above is incorporated.

FIG. 28 is a perspective view illustrating an embodiment (digital stillcamera) of the electronic apparatus according to the invention.

A display portion 1310 is provided on the back surface of a case 1302 ina digital still camera 1300 and is configured to perform display basedon an imaging signal of a CCD, and the display portion 1310 functions asa viewfinder for displaying a subject as an electronic image. A lightreceiving unit 1304 including an optical lens (image-capturing opticalsystem), a CCD or the like is provided on a front side (back side in thefigure) of the case 1302. When a photographer confirms a subject imagedisplayed on the display portion 1310 and presses a shutter button 1306,an image-capturing signal of the CCD at that time is transferred to bestored in the memory 1308. In such a digital still camera 1300, theinertial measurement device 2000 including the vibration element 1 (or1A, 1B, 1C, 1D, 1E) described above, and the measurement result of theinertial measurement device 2000 is used for camera shake correction,for example.

The electronic apparatus as described above includes the vibrationelement 1 (or 1A, 1B, 1C, 1D, 1E). According to such an electronicapparatus, it is possible to improve the characteristics (for example,reliability) of the electronic apparatus by utilizing the excellentcharacteristics of the vibration element 1 (or 1A, 1B, 1C, 1D, 1E).

In addition to the personal computer of FIG. 26 , the mobile phone ofFIG. 27 , and the digital still camera of FIG. 28 , the electronicapparatus may be applied to, for example, a smartphone, a tabletterminal, a clock (including a smart watch), an ink jet type ejectingdevice (for example, an ink jet printer), a wearable terminal such as ahead mounted display (HMD) a laptop type personal computer, atelevision, a video camera, a video tape recorder, a car navigationdevice, a pager, an electronic notebook (including electronic notebookwith a communication function), an electronic dictionary, a calculator,an electronic game device, a word processor, a workstation, a videophone, a TV monitor for crime prevention, an electronic binocular, a POSterminal, a medical device (for example, an electronic thermometer, ablood pressure monitor, a blood glucose meter, an electrocardiogrammeasuring device, an ultrasonic diagnostic device, an electronicendoscope), a fish finder, various measuring instruments, instruments(for example, instruments of an automobile, aircraft, rocket, and aship), a base station for a portable terminal, a flight simulator, andthe like.

5. Vehicle

FIG. 29 is a perspective view illustrating an embodiment (automobile) ofa vehicle according to the invention.

In an automobile 1500, the inertial measurement device 2000 includingthe vibration element 1 (or 1A, 1B, 1C, 1D, 1E) described above isincorporated, and an attitude of a vehicle body 1501 can be detected bythe inertial measurement device 2000, for example. The detection signalof the inertial measurement device 2000 is supplied to a vehicle bodyattitude control device 1502. The vehicle body attitude control device1502 can detect the attitude of the vehicle body 1501 based on thedetection signal and control hardness and softness of a suspensionaccording to the detection result or control brakes of individual wheels1503.

In addition, such attitude control can be utilized for a two-leg walkingrobot and a radio control helicopter (including drone). As describedabove, in order to realize attitude control of the vehicles, the inertiameasurement device 2000 is incorporated.

As described above, the automobile 1500 which is a vehicle includes thevibration element 1 (or 1A, 1B, 1C, 1D, 1E). According to such anautomobile 1500, it is possible to improve characteristics (for example,reliability) of the automobile 1500 by utilizing excellentcharacteristics of the vibration element 1 (or 1A, 1B, 1C, 1D, 1E).

Although the vibration element, the manufacturing method of thevibration element, the physical quantity sensor, the inertialmeasurement device, the electronic apparatus, and the vehicle accordingto the invention have been described based on the illustratedembodiments, the invention is not limited thereto, and the configurationof each unit can be replaced with any configuration having the samefunction. Further, any other constituent elements may be added to theinvention.

In the embodiments described above, the vibration element has aso-called double T-shape, H-shape, or two-legged tuning fork shape, butany device having a vibrating arm that vibrates in the in-planedirection may be used, and various forms, for example, a three-leggedtuning fork vibration element, an orthogonal type vibration element, aprismatic type vibration element, and the like may be adopted.

The entire disclosure of Japanese Patent Application No. 2018-009173filed Jan. 23, 2018 is expressly incorporated herein by reference.

What is claimed is:
 1. A vibration element comprising: three axesorthogonal to each other being defined as an X-axis, a Y-axis, and aZ-axis; a base; and a vibrating arm extending from the base to apositive side of the Y-axis, wherein the vibrating arm is configuredwith: a weight; an arm positioned between the base and the weight; and aweight film disposed on the weight, the weight includes a firstprincipal surface and a second principal surface that are perpendicularto the Z-axis and have a front and back relationship with each other,wherein a plane passing through a center of the arm in a Z-axisdirection along the Z-axis and parallel to an X-Y plane containing theX-axis and the Y-axis is defined as a center plane, a center of gravityof the weight is on a first principal surface side with respect to thecenter plane, and a center of gravity of the weight film is on a secondprincipal surface side with respect to the center surface, wherein theweight includes a first portion and a second portion, and the secondportion is thinner than the first portion in the Z-axis direction,wherein the second principal surface has a stepped shape formed by thefirst portion and the second portion, and the second portion is arrangedin a region from an end of the first portion on the positive side of theY axis to an end of the weight on the positive side of the Y axis in aplan view from the Z-axis direction.
 2. The vibration element accordingto claim 1, wherein the weight film is positioned on a second principalsurface side of the weight.
 3. The vibration element according to claim2, wherein the weight film is positioned on the first portion and thesecond portion.
 4. The vibration element according to claim 1, wherein awidth of the weight in an X-axis direction along the X-axis is widerthan a width of the arm in the X-axis direction in the plan view fromthe Z-axis direction.
 5. The vibration element according to claim 1,wherein the first principal surface is a flat surface.
 6. The vibrationelement according to claim 1, wherein the arm is plane-symmetric withrespect to the center plane.
 7. The vibration element according to claim1, wherein the arm a first arm, the weight is a first weight, thevibrating arm is a first vibrating arm, and the weight film is a firstweight film, and further comprising: a second vibrating arm extendingfrom the base to the positive side of the Y axis, wherein the secondvibrating arm is configured with: a second weight; a second armpositioned between the base and the second weight; and a second weightfilm disposed on the second weight, the second weight includes a thirdprincipal surface and a fourth principal surface that are perpendicularto the Z-axis and have a front and back relationship with each other,wherein a plane passing through a center of the second arm in the Z-axisdirection and parallel to the X-Y plane containing the X-axis and theY-axis is defined as a second center plane, a center of gravity of thesecond weight is on a third principal surface side with respect to thesecond center plane, and a center of gravity of the second weight filmis on a fourth principal surface side with respect to the second centerplane, wherein the second weight includes a third portion and a fourthportion, and the fourth portion is thinner than the third portion in theZ-axis direction, wherein the fourth principal surface has a steppedshape formed by the third portion and the fourth portion, and the fourthportion is arranged in a region from an end of the third portion on thepositive side of the Y axis to an end of the second weight on thepositive side of the Y axis in the plan view from the Z-axis direction.8. The vibration element according to claim 7, wherein the base isconfigured with: a base body; and a connecting arm extending from thebase body, and further comprising: a drive arm that extends from theconnecting arm and that is subjected to drive vibration; and a detectionarm extending from the base body and deforming in response to inertialforce; wherein the drive arm includes the first vibrating arm and thesecond vibrating arm.
 9. The vibration element according to claim 7,further comprising: a drive arm extending from the base and that issubjected to drive vibration; and a detection arm extending from thebase to a negative side of the Y axis and deforming in response toinertial force; wherein the drive arm includes the first vibrating armand the second vibrating arm.
 10. The vibration element according toclaim 1, wherein the weight film comprises: a film thickness portion;and a film thin portion that is thinner than the film thickness portion.11. A physical quantity sensor comprising: the vibration elementaccording to claim 1; and a package which accommodates the vibrationelement.
 12. An inertial measurement unit comprising: the physicalquantity sensor according to claim 11; and a circuit which iselectrically connected to the physical quantity sensor.
 13. Anelectronic apparatus comprising: the vibration element according toclaim
 1. 14. A vehicle comprising: the vibration element to claim 1.